How Many Hazardous Material Classes Are There?
There are nine distinct hazard classes, each representing a specific type of dangerous substance or article capable of posing a risk to health, safety, property, or the environment during transportation. These classes are universally recognized and used to categorize hazardous materials for shipping, handling, and storage.
Understanding the Nine Hazard Classes
Hazardous materials, often referred to as hazmat, are substances that present inherent dangers and require specialized handling. Identifying these materials correctly is crucial for safe transportation. The nine hazard classes serve as the foundation for regulatory frameworks worldwide. Understanding the characteristics of each class is vital for anyone involved in the transportation, storage, and emergency response related to hazardous materials.
Class 1: Explosives
Explosives are substances or articles that are capable of producing a sudden expansion of gas resulting in a rapid increase in pressure and/or an extremely rapid liberation of heat when subjected to shock, friction, heat, or detonation. Examples include dynamite, fireworks, and ammunition. Class 1 is further subdivided into divisions based on the type of explosion hazard.
Class 2: Gases
Gases are materials that are in a gaseous state at 20°C (68°F) and a pressure of 101.3 kPa (14.7 psi). This class includes compressed gases, liquefied gases, dissolved gases, refrigerated liquefied gases, and gas mixtures. Class 2 is divided into three divisions:
- Division 2.1: Flammable Gases: These gases can easily ignite and burn rapidly. Examples include propane and butane.
- Division 2.2: Non-Flammable, Non-Toxic Gases: These gases do not easily burn and are not poisonous, but they can displace oxygen and cause asphyxiation. Examples include nitrogen and carbon dioxide.
- Division 2.3: Toxic Gases: These gases are poisonous and can be harmful or fatal if inhaled. Examples include chlorine and phosgene.
Class 3: Flammable Liquids
Flammable liquids are liquids, or mixtures of liquids, or liquids containing solids in solution or suspension that give off a flammable vapor at temperatures not more than 60°C (140°F). Examples include gasoline, acetone, and paint thinner.
Class 4: Flammable Solids; Substances Liable to Spontaneous Combustion; Substances Which, on Contact with Water, Emit Flammable Gases
This class includes three divisions related to solid flammability.
- Division 4.1: Flammable Solids: These are readily combustible solids or solids that may cause or contribute to fire through friction. Examples include matches and sulfur.
- Division 4.2: Substances Liable to Spontaneous Combustion: These are substances that can spontaneously heat up and ignite in air. Examples include white phosphorus and oily rags.
- Division 4.3: Substances Which, on Contact with Water, Emit Flammable Gases: These substances react dangerously with water, releasing flammable gases. Examples include sodium and calcium carbide.
Class 5: Oxidizing Substances and Organic Peroxides
Oxidizing substances can cause or contribute to the combustion of other materials. Organic peroxides are thermally unstable substances that may undergo self-accelerating decomposition. Class 5 is divided into two divisions:
- Division 5.1: Oxidizing Substances: Examples include ammonium nitrate and potassium perchlorate.
- Division 5.2: Organic Peroxides: Examples include methyl ethyl ketone peroxide and benzoyl peroxide.
Class 6: Toxic Substances and Infectious Substances
Toxic substances are substances that are poisonous and can cause death or serious injury if inhaled, swallowed, or absorbed through the skin. Infectious substances contain pathogens that can cause disease in humans or animals. Class 6 is divided into two divisions:
- Division 6.1: Toxic Substances: Examples include cyanide and arsenic.
- Division 6.2: Infectious Substances: Examples include cultures of microorganisms and medical waste.
Class 7: Radioactive Material
Radioactive material contains radionuclides where both the activity concentration and the total activity in the consignment exceed specified values. Examples include uranium and plutonium.
Class 8: Corrosive Substances
Corrosive substances are substances that can cause visible destruction or irreversible alterations to human skin tissue, or cause a severe corrosion rate on steel or aluminum. Examples include sulfuric acid and sodium hydroxide.
Class 9: Miscellaneous Dangerous Goods
Miscellaneous dangerous goods are substances or articles which present a danger during transport but are not covered by any of the other hazard classes. This is a catch-all class for items that don’t fit neatly into the other eight. Examples include asbestos and lithium batteries.
Frequently Asked Questions (FAQs)
FAQ 1: What is the purpose of hazard classes?
The primary purpose of hazard classes is to categorize hazardous materials based on the specific risks they pose. This classification enables the development and implementation of appropriate safety measures for transportation, handling, and storage, minimizing the risk of accidents and incidents.
FAQ 2: How are hazard classes identified?
Hazard classes are identified through testing and evaluation of the substance or article in question. These tests assess various properties, such as flammability, toxicity, corrosivity, and reactivity. Results are then compared to established criteria to determine the appropriate hazard class.
FAQ 3: What are UN numbers and how do they relate to hazard classes?
UN numbers (United Nations numbers) are four-digit numbers assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods to identify hazardous substances and articles. Each UN number is associated with a specific hazard class and a proper shipping name. They are crucial for identifying hazardous materials internationally.
FAQ 4: What is a packing group, and how does it relate to hazard classes?
Packing groups indicate the degree of danger presented by a hazardous material within a specific hazard class. There are three packing groups:
- Packing Group I: High danger
- Packing Group II: Medium danger
- Packing Group III: Minor danger
The packing group determines the type of packaging required for safe transportation.
FAQ 5: What are hazard communication labels and placards, and why are they important?
Hazard communication labels are small labels affixed to individual packages containing hazardous materials. They display the hazard class symbol, UN number, and proper shipping name. Placards are larger diamond-shaped signs displayed on vehicles and containers transporting hazardous materials. Both labels and placards are vital for visually communicating the hazards present, allowing for appropriate precautions to be taken during transportation and handling.
FAQ 6: What regulations govern the transportation of hazardous materials?
The transportation of hazardous materials is governed by various regulations, depending on the mode of transport and geographical location. In the United States, the Department of Transportation (DOT) enforces regulations outlined in Title 49 of the Code of Federal Regulations (49 CFR). Internationally, regulations are based on the United Nations Recommendations on the Transport of Dangerous Goods.
FAQ 7: What training is required for individuals handling hazardous materials?
Individuals involved in the transportation of hazardous materials are required to undergo hazmat training. This training covers hazard recognition, handling procedures, emergency response, and regulatory requirements. The specific training requirements depend on the individual’s role and the type of hazardous materials handled.
FAQ 8: What should I do in case of a hazmat spill or accident?
In the event of a hazmat spill or accident, the first priority is to ensure personal safety and the safety of others. Evacuate the area if necessary, and contact emergency services immediately. Provide as much information as possible, including the location of the incident, the type of hazardous material involved (identified by its UN number, if possible), and the extent of the spill or release.
FAQ 9: What is the difference between a “hazardous material” and a “hazardous waste”?
While both involve hazardous substances, the distinction lies in their intended use or disposal. A hazardous material is a substance being transported for use or distribution. A hazardous waste, on the other hand, is a discarded material that exhibits hazardous characteristics and is subject to regulations governing its disposal.
FAQ 10: Where can I find more information about specific hazardous materials and their properties?
Detailed information about specific hazardous materials can be found in Safety Data Sheets (SDS), formerly known as Material Safety Data Sheets (MSDS). SDSs provide comprehensive information about the properties, hazards, handling procedures, and emergency response measures for individual substances.
FAQ 11: How are lithium batteries classified and transported?
Lithium batteries are classified as Class 9, Miscellaneous Dangerous Goods. However, their transportation is subject to specific regulations due to the potential for overheating and fire. These regulations address packaging, labeling, and quantity limitations.
FAQ 12: What is the Globally Harmonized System (GHS), and how does it relate to hazard classes?
The Globally Harmonized System of Classification and Labelling of Chemicals (GHS) is an internationally agreed-upon system for classifying and labeling chemicals. While GHS uses different terminology and hazard categories, it aims to align with the principles underlying hazard classes, promoting consistent hazard communication worldwide. The GHS utilizes pictograms and signal words to communicate hazards, supplementing the existing hazard class system for greater clarity and ease of understanding.